Update docs according to PR #5127

misplaced CV_WRAP statement lead to not exposing EM::getCovs() to python/java/matlab wrappers

add a CV_OUT to return the covs properly

2. Algorithm::load/save added (moved from StatModel)
3. copyrights updated; added copyright/licensing info for ffmpeg
4. some warnings from Xcode 6.x are fixed

REG_NONE defined in ml.hpp conflicts with defined in Winnt.h

- fixed one BiB record
- moved algorithms overview to separate page
- added docs for some enumerations
- fixed some small documentation errors

Removed the "FileStorage::FORMAT_XML" to generalize format of the String
model.

Re-edited the documentation again.

Attempting to re-editing the documentation, to satisfy buildbot error
status.

Edited previous code to change tabs into spaces.

Added a method "loadFromString" which is based on the "load" one. It
allow to directly pass the XML string which can be usefull and faster
when you have a huge file in a variable.

- Reworked documentation to reflect actual code
- Removed some unused variables
- Removed unnecessary 'cv::' modifiers